The present invention relates to an electric water warming system capable of feeding hot water from a hot water storage tank and is particularly concerned with an electric water warmer for which the hot water storage tank is effectively prevented from being emptied.
An electric water warmer of this kind operates such that water fed into a hot water storage tank is heated on, for example, a cheap late-night power to increase a temperature of a fed water and is stored in the storage tank as a hot water.
A typical example of the electric water warmer of this character comprises a hot water tank having a lower bottom portion to which a water feed pipe is connected and an upper top portion to which a water flow-out pipe is connected. One heater is arranged substantially horizontally at a lower portion within the hot water storage tank to heat water fed into the tank to a high temperature. The highly heated water is stored in the storage tank. More concretely, the water fed into the water storage tank and stored therein is heated by current conduction of the heater to gradually increase the temperature of the fed water in a substantially linearly slightly increasing temperature curve as a function of heating time. The thus heated hot water is stored in the hot water storage tank for almost filling in the entire area from the tank lower portion to the tank upper portion.
The electric water warmer of the conventional type described is constructed such that one heater is disposed near the bottom portion of the hot water storage tank, water fed into the hot water storage tank is heated by the heater, and the heated hot water is supplied from the flow-out pipe connected to the top of the hot water storage tank. Therefore, if the hot water is fed in a large amount of volume through the flow-out pipe and so consumed, there may be caused a case where the the hot water in the tank is flown out unexpectedly, or if a current is conducted to the heater after the hot water is left as a residue in the hot water storage tank, the heater comes to heat almost all quantity of the residue within the hot water storage tank, thus a necessary amount of the hot water cannot be secured quickly and a sudden exhaustion thereof cannot be coped with quickly and pertinently.